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Lecture 18

The document discusses the RC Half Wave Triggering of SCR, detailing the circuit operation during both the negative and positive half cycles. It explains how the capacitor charges and discharges, triggering the SCR while preventing negative voltage across the gate terminal. The SCR can be controlled for a 180-degree range, offering better control compared to conventional R triggering circuits.

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Suji Krish
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2 views2 pages

Lecture 18

The document discusses the RC Half Wave Triggering of SCR, detailing the circuit operation during both the negative and positive half cycles. It explains how the capacitor charges and discharges, triggering the SCR while preventing negative voltage across the gate terminal. The SCR can be controlled for a 180-degree range, offering better control compared to conventional R triggering circuits.

Uploaded by

Suji Krish
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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Lecture 18: RC Half Wave Triggering of SCR

Video Link: https://youtu.be/xZ7FZkFHEMY


RC Half Wave Triggering of SCR:
Fig 1 shows the circuit diagram of RC Half Wave Triggering of SCR.

Fig 1: Circuit Diagram of RC Half Wave Triggering of SCR


• During the negative half cycle the capacitor charges to negative polarity through the
diode D2 as shown in Fig 2. The flow of current is through the path indicated with the
red arrowhead.

Fig 2: Working during negative half cycle


• During positive half cycle, the capacitor discharges through the resistor R as shown in
Fig 3 (Red arrow head). Once the energy is discharged, the capacitor starts charging to
positive voltage (through the green arrow head). Once the capacitor charges to the gate
voltage, the gate current is provided through the diode D1.

Fig 3: Working during positive half cycle


Mail ID: electronicsmaddy@gmail.com
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Lecture 18: RC Half Wave Triggering of SCR
Video Link: https://youtu.be/xZ7FZkFHEMY
• Diode D1 also prevents negative capacitor voltage to appear across the gate terminal of
SCR. Fig 4 shows the waveform of the RC triggering circuit of SCR. It can be observed
that the SCR can be triggered for 180-degree range. Hence it is having much better
control over the conventional R triggering circuit of SCR.
• Since the SCR can be controlled for only one-half cycle range, it is called as Half wave
RC triggering circuit of SCR.

Fig 4: Waveform of RC Half Wave Triggering of SCR


• For zero output (i.e RC Half Wave Triggering of SCR maximum firing angle), the
following relation holds good:
1.3
RC ≥
2𝑓

Mail ID: electronicsmaddy@gmail.com


Instagram DM: Electronics Maddy

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